How Long Do Solar Street Light Lithium Batteries Last?

Nowadays, most solar street light lithium batteries use power cells with a service life of more than 15 years. The lifespan of a solar street light powered by a lithium battery made of cascade cells is 10 to 15 years. And solar street light batteries made of brand-new power cells can last as long as 15 to 20 years. How long exactly is the lifespan of a solar street light lithium battery?

How to calculate the lifespan of a solar street light lithium battery?

Data of colloidal lead-acid batteries

Let’s put aside the influence of the environment and default to a constant temperature of 25 degrees. From the above chart, we can see that the cycle life of lead-acid batteries is different at different discharge depths. When the discharge depth is 100%, the cycle time is approximately 280. At 50% DOD, about 820 cycles, and at 30% DOD, 1200 cycles.

The cycle life curves of lithium batteries

The aim of the test is to count the cycle life of ternary lithium batteries from LG, Samsung, Panasonic, and Ningde. There are soft-pack, cylindrical, and square batteries. The shortest life is Panasonic 18650, which can cycle for 500 times, followed by Samsung SDI with 1000 cycle times, LG with 1450 cycle times, and Ningde with the longest 1800 cycle times. Note that these batteries all work at 100% DOD and in an environment of 25 degrees Celsius.

With the iteration of lithium batteries, their lifespan becomes longer. Now the cycle time of basic power ternary lithium batteries on the market can reach 2000, while iron lithium batteries can have 4000 cycle times.

In summary, we can take the average value of the above ternary lithium batteries as their cycle time, which is 1350. The cycle time of iron and lithium is twice that of ternary, which is 2700. At 100% DOD, the cycle life of ternary is 4.8 times that of colloid, and that of iron-lithium is 9.6 times that of colloid. Another feature of lithium batteries is that their lifespan increases with the depth of discharge. By calculating in proportion, we can get the following results:

The service life of batteries for cascade use

Above is the lifespan of new power lithium batteries for solar street lights; how long is the service life of the batteries for cascade use? Usually, the battery with a 30% power attenuation will retire. Then, these batteries will be classified according to their quality for cascade use. While calculating their lifespan, we can minus 30% of the cycle times and then calculate it according to 1 cycle per day (actually, the battery cannot work for a cycle in 1 day) to get the lifespan of the battery.

Why is the lifespan of lithium batteries for solar street lights so short?

The ideal lifespan of lithium batteries for solar street lights should be as long as 8 to 22 years. However, the lithium batteries some customers bought can only work for 1 to 3 years. The choice of materials and production methods is the primary cause of the short lifespan.

Selection of materials

• Energy and power batteries: In terms of performance, there are two types of lithium batteries on the market: energy and power batteries. Most of the energy batteries are brand new, but their quality is low because of the materials and production processes. Like general colloidal batteries, the lifespan of energy lithium batteries is only 3 to 5 years, while the lifespan of power batteries is more than 10 years.
• Selection of batteries for cascade use: Although according to the standards,the power batteries should retire when their power decays by 30%, there are many power batteries for cascade use that cannot meet the requirements. As a solar street light lithium battery manufacturer, it is necessary to have the ability to select batteries that meet standards.
• Selection of protection board: Choose the protection board with balance function from big brands so that it won’t affect the lifespan of the battery.

Important processes for high-quality solar street light lithium batteries

• Screening:Each battery cell must be screened so that the batteries with substandard parameters such as capacity, charge and discharge curve, and voltage can be picked out.
• Waiting:The battery cells should be kept in the cabinets for 7 days.
• Agingtest: By simulating the working solar street light system, test the battery packs, protection boards, controllers, cables, light sources, and other components of the entire solar street light system to solve as many faults as possible in the factory.

Only a few solar street light manufacturers on the market can choose high-quality materials and meet the requirements of the producing processes. This is why the lifespan of solar street light lithium batteries on the market is short.

Conclusions

We have provided data of the cycle times of colloid lead-acid, ternary lithium, and iron-lithium batteries at different discharge depths. In theory, under a constant temperature of 25 °C and at 100% DOD, the ternary lithium battery can last for over 3 years, and the iron-lithium battery can work for over 7 years. However, in actual use, the lifespan of the battery is also influenced by the environment and the system design. When the solar battery cannot store enough energy to provide sufficient lighting, you need to replace them in time. Professional manufacturers like Casyoo can take measures adapted to certain conditions and provide a complete set of detailed system designs. If you want your batteries to have a lifespan that is close to their theoretical value, contact us now!